U.S. patent number 5,340,376 [Application Number 07/793,355] was granted by the patent office on 1994-08-23 for controlled-release microbe nutrients and method for bioremediation.
This patent grant is currently assigned to The Sierra Horticultural Products Company. Invention is credited to John Cunningham.
United States Patent |
5,340,376 |
Cunningham |
August 23, 1994 |
Controlled-release microbe nutrients and method for
bioremediation
Abstract
A controlled-release nutrient source is added at a low level to
a bioremediation environment to enhance microorganism growth and
activity and promote the effectiveness of the bioremediation in
removing environmental contaminants.
Inventors: |
Cunningham; John (Tracy,
CA) |
Assignee: |
The Sierra Horticultural Products
Company (Milpitas, CA)
|
Family
ID: |
24133991 |
Appl.
No.: |
07/793,355 |
Filed: |
January 8, 1992 |
PCT
Filed: |
June 06, 1991 |
PCT No.: |
PCT/US91/03986 |
371
Date: |
January 08, 1992 |
102(e)
Date: |
January 08, 1992 |
PCT
Pub. No.: |
WO92/19544 |
PCT
Pub. Date: |
November 12, 1992 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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535393 |
Jun 8, 1990 |
|
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Current U.S.
Class: |
71/6; 210/610;
435/262; 71/64.11; 71/903 |
Current CPC
Class: |
B09C
1/10 (20130101); C02F 3/34 (20130101); C12N
1/20 (20130101); C12N 1/38 (20130101); Y10S
71/903 (20130101) |
Current International
Class: |
A62D
3/00 (20060101); B09C 1/10 (20060101); C02F
3/34 (20060101); C12N 1/20 (20060101); C12N
1/38 (20060101); C05F 011/08 (); C05F 003/00 () |
Field of
Search: |
;71/903,64.11,6-8
;210/610,611 ;435/262 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
Genetic Engineering News (Nov./Dec. 1989) 9(10):3. .
Busch, Aerobic Biological Treatment of Waste Waters, Oligodynamics
Press, Houston, (1971) pp. 107-111..
|
Primary Examiner: Lander; Ferris
Attorney, Agent or Firm: Morrison & Foerster
Parent Case Text
This application is a continuation-in-part of U.S. Ser. No.
535,393, filed Jun. 8, 1990 and abandoned on Jan. 9, 1992.
Claims
What is claimed:
1. In a biological remediation process wherein microorganisms are
employed to degrade contaminating organic compounds present within
an environment over an extended period of time, the improvement
which comprises applying to said environment a low-level of
controlled-release source of microorganisms nutrients capable of
continuously supplying an effective microorganism growth-and
activity-promoting level of nutrients to the microorganisms over a
period of time of at least about two months, said
controlled-release source of microorganism nutrients being in the
form of coated solid particles each having a core of water soluble
microorganism nutrients encapsulated in a release rate-controlling
coating and where said particles are admixed in the environment at
a level of 0.25 to 3 pounds per cubic yard of environment.
2. The process of claim 1 wherein said environment is a soil
environment.
3. The process of claim 2 wherein said nutrients are applied to
said soil in its natural environment.
4. The process of claim 2 wherein said soil is moved from its
natural environment.
5. The process of claim 2 wherein said soil is mixed with a
composting material.
6. The process of claim 2 wherein said soil is slurried in an
aqueous environment.
7. The process of claim 1 wherein said environment is an aqueous
environment.
8. The process of claim 7 wherein said aqueous environment is any
naturally occurring body of water.
9. The process of claim 7 wherein said aqueous environment is any
artificially formed body of water.
10. The process of claim 7 wherein said aqueous environment is
groundwater.
11. The process of claim 7 wherein said aqueous environment is an
effluent from an industrial process.
12. The process of claim 7 wherein said aqueous environment is
municipal waste water.
13. The process of claim 1 wherein said nutrients comprise nitrogen
and phosphorus.
14. The process of claim 13 wherein said nutrients additionally
comprise sulfur.
15. The process of claim 13 wherein said nutrient additionally
comprises micronutrients.
16. The process of claim 13 wherein said nutrients additionally
comprise a vitamin.
17. The process of claim 13 wherein said nutrients additionally
comprise a buffer.
18. The process of claim 13 wherein said controlled-release
nutrients are comprised of water soluble macronutrients
encapsulated in a linseed oil/dicyclopentadiene resin.
19. In a biological remediation process wherein microorganisms are
employed to degrade contaminating organic compounds present within
a soil environment over an extended period of time, the improvement
which comprises admixing with said soil environment from about 0.25
to 3 pounds per cubic yard of soil environment of
controlled-release source of microorganisms nutrients capable of
continuously supplying an effective microorganism growth-and
activity-promoting level of nutrients to the microorganisms over a
period of time of at least about two months.
Description
FIELD OF THE INVENTION
This invention relates to improvements in biological remediation
(bioremediation) efficiencies and improvements to the environmental
soundness of the bioremediation approach to contamination cleanup.
More particularly, it relates to improved nutrient delivery systems
which reduce nutrient losses in open systems such as the ones found
in most bioremediation operations. These nutrient delivery systems
are amenable to both soil and water applications and are
particularly helpful in reducing labor costs associated with
nutrient application and also in reducing the potential for
environmental damage due to nutrient run-off.
BACKGROUND INFORMATION
Bioremediation refers to the conversion of toxic environment
contaminating compounds into innocuous substances by way of
microbial digestion. Bioremediation has been successfully used to
treat contaminated soil in above-ground treatment systems,
above-ground slurry bioreactors, slurry pits, above-ground soil
heaps, composting material, and in situ. A good example of in situ
soil treatment came following the Exxon Valdez oil spill in Prince
William Sound, Alaska. This oil contaminated miles of Alaskan
shoreline and an approximately 70 mile section of shoreline was
treated using bioremediation. This remediation process as it was
employed focused on enhancing the indigenous microorganisms' growth
and oil degrading activities through the application of
nutrients.
Representative disclosures of bioremediation process include U.S.
Pat. No. 4,035,289, to Michel Guillerme et al., which discloses a
method for removing hydrocarbon residues from the effluents from
oil well drilling. This method involves culturing microorganisms in
a portion of the effluent and then adding the portion back to the
remainder to degrade the hydrocarbons. Genetic Engineering News,
vol. 9, No. 10 (Nov.-Dec. 1989) at page 3 presents a good example
of the in situ bioremediation processes used to assist the clean-up
of the Exxon Valdez oil spill in Prince William Sound, Alaska.
It is known that speeding the bioremediation process, by promoting
the growth and activity of the waste-degrading microorganisms is
desirable. In most situations the microorganisms naturally present
in the soil and groundwater are capable of degrading the
contaminating compounds. For a successful remediation, the
bioremediator must enhance the growth and activity of these
naturally occurring microorganisms. To that end, it is understood
that supplying the microorganisms with nutrients and advantageous
environmental conditions is beneficial. Just noted U.S. Pat. No.
4,035,289 teaches the addition of nitrogen and phosphorus sources
to its culturing medium. U.S. Pat. No. 4,727,031 to Richard A.
Brown et al., describes a composition of nutrients and a method of
using the composition to stimulate the growth of aerobic bacteria,
and particularly bacteria capable of hazardous waste degradation.
This patent makes reference to Busch, Aerobic Biological Treatment
of Waste Waters, Oligodynamics Press, Houston (1971), at page 107,
for teaching that phosphorus and nitrogen are critical
growth-limiting nutrients and when not present must be added to
aerobic bacteria, such as those found naturally occurring in soil
and water environments. Other similar disclosures of bioremediation
include U.S. Pat. No. 3,846,290 to Richard Raymond, which discloses
the advantageous injection of nutrients into subsurface water
supplies to reduce contaminating hydrocarbons; U.S. Pat. No.
4,401,569 to Vidyut Jhaveri et al., which similarly shows injecting
nutrients into the ground to enhance microbial action on
contaminants; U.S. Pat. No. 4,925,802 to Michael Nelson et al.,
which shows adding an amino acid to bioremediation systems; U.S.
Pat. No. 4,849,360 to Edward Azarowicz, which shows a multitank
digestion process for degrading oily wastes; and U.S. Pat. No.
4,493,895 to Joseph F. Colaruotolo et al., which shows particular
microorganisms which are capable of dissimilating halogenated
compounds into the natural carbon cycle.
In general, therefore, bioremediations are speeded by adding
nutrients, pH adjusters, and if aerobic microorganisms are used,
oxygen to the soil and/or water of interest. By adjusting these
parameters the indigenous microorganisms will multiply and become
more active resulting in faster waste degradation. It only becomes
necessary to add "foreign" microorganisms to the contaminated
environment if the indigenous microorganisms do not posses the
genes needed to create the enzymes necessary to degrade the
contaminant, if the contaminant is at such a high concentration as
to be toxic to the natural microorganisms, or if the contaminant
concentration is so low the natural level of microorganisms cannot
further degrade it to an acceptable level.
In most cases, bioremediations are performed in environments such
as on site locations which can be classified as open systems. In
the case of biodegradation in a closed environment, such as a batch
bioreactor, it is sufficient to use an aqueous culture medium which
completely and immediately supplies the microorganisms with the
various nutrients required to increase degradation rates. These
various nutrient elements are discussed in U.S. Pat. Nos. 4,035,289
and 4,727,031 which were noted above. Nutrient needs in open
systems cannot be efficiently filled using the teachings of U.S.
Pat. No. 4,035,289. This is because this patent shows the
application of nutrient compounds which have virtually no ability
to remain in the microorganisms' environment for extended periods
in an open system. In this situation, it is necessary to apply
these nutrients repeatedly to the open system throughout the
remediation's duration.
The resulting depletion-reapplication cycle puts the microorganisms
in a stressed state, and the microbes degradative efficiency is
reduced. In addition, the washing away of the nutrients, from the
point of application, is wasteful and may actually add to the
environmental problem. One example of a nutrient runoff problem is
blue baby syndrome which is caused by nitrates contaminating
"potable" water supplies. This nutrient loss may be avoided to some
extent by supplying nutrients in a form which can be associated or
bound with the contaminant, such as a hydrocarbon waste, to provide
a localized growth medium for the microorganisms.
U.S. Pat. No. 3,943,066, to Pierre Fusey, discloses a method for
nutrient-waste mass association using an aqueous biodegradable
emulsion of nitrogen- and phosphorus-containing substances with the
hydrocarbon waste. In U.S. Pat. No. 4,460,692, to Jacques Tellier
et al., a lipophilic microemulsion of an aqueous nutrient solution
is applied in a layer upon the waste mass. These methods provide a
way to associate essential nutrients onto the surface of the
organic waste, but do not provide a controlled rate of nutrient
release to the microorganisms' environment. In another, related
disclosure, U.S. Pat. No. 4,401,762, also to Jacques Tellier et
al., describes a process of culturing microorganisms using a
microemulsion of nutrients and the use of this process in
biodegradation settings.
The present invention addresses the problem of nutrient delivery to
bioremediation environments by using controlled-release nutrient
delivery systems engineered specifically for microorganisms.
Controlled-release compositions have been used heretofore to
provide nutrients to growing organisms, such as plants. See, for
example, U.S. Pat. No. 4,657,576 to Johannes Lambie, which
discloses a fertilizer composition for releasing nutrients to
plants throughout the growing season; U.S. Pat. Nos. 3,300,293 and
3,252,786 to Andrew Bozzelli et al., which each relate to a
slow-release fertilizer composition comprising a dispersion of
urea-wax adduct in wax and its use fertilizing crops; U.S. Pat. No.
3,259,482 to Louis Hansen, which describes a slow-release
fertilizer having a plurality of epoxy-polyester resin coatings and
its use with plants; U.S. Pat. No. 3,232,739 to Steven Belak, which
describes a polyurethane foam extended with free urea and the
ability of the foams to supply urea fertilization to a plant
throughout a long period of time; U.S. Pat. No. 3,252,786 to Andrew
Bozzelli et al., which involves slow-release fertilizer
compositions containing urea, wax, rosin, and optionally asphalt,
and their use in fertilization processes; U.S. Pat. No. 3,475,154
to Haruhiro Kato et al., which describes resin-coated fertilizer
particles and their use in garden settings; U.S. Pat. No. 4,120,685
to Silvio Vargiu et al., which describes fertilizers capable of
achieving slow-release of nitrogen from urea-formaldehyde mixtures;
U.S. Pat. No. 4,563,208 to Peter Backlund, which shows that
fertilizer particles can be covered with a reaction product of urea
and metal oxides; U.S. Pat. No. 4,210,437 to Robert Windgassen et
al., which shows liquid fertilizer compositions which provide
sulfur, nitrogen and micronutrient metals; and U.S. Pat. No.
4,756,738 to William J. Detroit, which shows a copolymer matrix
which is capable of gradually releasing fertilizer.
Additional patents of note are U.S. Pat. No. 4,111,201, to Felix
Theeuwes, and U.S. Pat. No. 3,952,741, to Richard Baker, which
discloses devices capable of osmotically delivering beneficial
agents. While for the most part, these patents are directed to
delivering pharmaceutical agents to patients, they do generally
include the delivery of any "active agent", including in the case
of U.S. Pat. No. 4,111,201 microorganism attenuators, fermentation
agents, nutrients and other agents that "benefit the environment of
use" and in the case of U.S. Pat. No. 3,952,741, any agent in any
way affecting any biological entity.
The current invention improves the efficiency of bioremediations in
soil and/or aqueous environments by providing controlled-release
compositions which supply nutrients to the microorganisms in a
regulated, environmentally sound, and cost effective manner.
STATEMENT OF THE INVENTION
An improvement in bioremediation processes has now been found. Such
bioremediation processes are those in which an organic
chemical-contaminated soil or aqueous environment is remediated by
the digestive action of microorganisms, on the chemical
contaminant, within the environment. This digestive action
typically takes two or more months before acceptable levels of
degradation have taken place and the contaminated environment is no
longer considered a threat. The improvement provided by the present
invention involves applying to said environment, and thus the
degrading microorganisms present therein, a controlled-release
source of microorganism nutrients at a low level and optionally
vitamins and/or nutrients which double as buffering agents (to keep
the environment surrounding the product at a pH which is compatible
with the growth and activity of the desired microorganisms). This
controlled-release source is capable of continuously supplying an
effective level of microorganism-promoting nutrients, some of which
may double as buffering agents, to the contaminated environment
during the prolonged period of digestive action. These prolonged
periods of bioremediation action are those typically associated
with this process in the art, such as at least about 1 week and
more commonly from 1 to 100 weeks, especially from 10 to 40 weeks.
The controlled-release source of nutrients typically releases
nitrogen and/or phosphorus and/or sulfur to the microorganisms.
This invention can find application in bioremediations performed in
soils and/or aqueous environments which have become contaminated
with aliphatic hydrocarbons. It can also find use in soils and/or
aqueous environments which have been contaminated with aromatic
hydrocarbons, including halogenated aromatic, polynuclear aromatic,
polychlorinated biphenyls (PCB), trichloroethylene (TCE),
percholorethylene, various pesticides, various herbicides, and with
any chemical deemed to be bioremediable.
The invention can be used in soil environments and in aqueous
environments. These environments can be open or closed. The soil
environments include soil in above-ground treatment systems,
above-ground slurry bioreactors, slurry pits, above-ground soil
heaps, composting material, in situ, and the like. The aqueous
environments include lakes, ponds, rivers, slurry pits,
above-ground slurry bioreactors, bioreactors, ground water, and the
like.
In addition to the macronutrients (nitrogen, phosphorus, and
sulfur), the invention can serve to deliver essential
micronutrients such as micronutrient metals to the microorganisms
as well. In another embodiment additional growth promoters, a
vitamin source, for example yeast extract, can be incorporated into
the controlled-release composition or administered concomitantly to
additionally promote the vitality and growth of the microorganisms.
Thus, in additional aspects, this invention can deliver in a
controlled-sustained manner macronutrients, micronutrients,
buffers, vitamins and the like or any combination thereof, to the
bioremediation microorganisms.
In a preferred embodiment, this invention provides significantly
enhanced levels of bioremediation by the unexpected feature of
using lower levels of nutrients--that is, lower use levels of
nutrients at sustained levels give higher activity than is achieved
at higher nutrient levels.
As will be apparent, the present invention is highly advantageous
when applied to environments requiring bioremediation activities in
that it provides a way to efficiently deliver essential nutrients,
in an environmentally sound way, to the waste-degrading
microorganisms throughout the entire remediation without the
expensive, wasteful, labor intensive multiple reapplications called
for in methods of the prior art. Surprisingly, in order to obtain
the most efficient bioremediation, the concentration of the
nutrients in the soil is maintained at a lower level than suggested
by the prior art.
BRIEF DESCRIPTION OF THE DRAWINGS
This invention will be described with reference being made to the
accompanying drawings in which:
FIG. 1 is a graph showing bacterial levels in soil over time at
various levels and types of nutrient addition in accord and not in
accord with this invention;
FIG. 2 is a three line graph showing diesel fuel contamination
levels at various nutrient release rates in accord and not in
accord with this invention over a 100-day trial period of
bioremediation; and
FIGS. 3-6 are a series of bar graphs comparing the levels of
various hydrocarbon contaminants in an oil-fouled environment at a
starting point (FIG. 3), after one month (FIG. 4), after about two
months (FIG. 5), and after about three months (FIG. 6), when the
present invention is practiced and when control conditions are
imposed.
DESCRIPTION OF PREFERRED EMBODIMENTS
The Macronutrients
The materials employed in the present invention deliver nitrogen,
phosphorus, and/or sulfur as macronutrients to the bioremediation
microorganisms. Nitrogen can be delivered as nitrate, ammonium,
urea or cyanamide. Phosphorus is typically delivered as phosphate.
Sulfur is generally delivered as sulfate. Potassium, a usual
component of plant nutrient material, may be present but generally
is not required. The macronutrients employed to make up the
controlled-release product are normally standard fertilizer
materials and can include urea, ammonium nitrate, ammonium
phosphates, ammonium sulfate, calcium nitrate, calcium cyanamide,
sodium nitrate, calcium phosphates, single superphosphate, triple
superphosphate, potassium nitrate, and potassium sulfate. These
materials are highly water soluble with the exception of calcium
cyanamide and calcium phosphates, and if employed without a
controlled-release coating, would rapidly dissolve in and be
dissipated in an open environment. The amounts of nitrogen,
phosphorus, and sulfur can be varied in the product to give
compositions having from 0 to 40 percent nitrogen, from 0 to 40
percent phosphorus, and from 0 to 20 percent sulfur by weight based
on the overall micronutrient composition. Preferred ranges are from
10 to 40 percent nitrogen and 2 to 20 percent phosphorous and 0 to
10 percent by weight sulphur. In one preferred embodiment, the
total nitrogen is approximately 28 percent nitrogen, and the
phosphorous level is 3.5 percent or 8 percent in P.sub.2 O.sub.5
form. This type of product would be referred to as a 28-8-0 (0
being potassium in K.sub.2 O form) product in typical fertilizer
nomenclature. At this time, it is accepted in the bioremediation
industry that the product should release 1 to 10 parts nitrogen per
part by weight phosphorus.
Micronutrients
The materials employed in the present invention may also contain
micronutrients to promote the growth and activity of the
microorganisms. These micronutrients can include all those
materials known by those in the art to be essential to the
microorganisms. These can include metals, for example, magnesium,
iron, manganese, calcium, and the like. The micronutrients are
optional, and if present, are present in very low levels of
typically less than 1 percent and more likely less than 0.1 percent
by weight, such as from 1 to about 500 ppm by weight. These
materials can be made to release at the same rate as the
macronutrients or faster than the macronutrients depending upon the
needs of the microorganisms. A faster release can be attained by
coating these materials on the outside of particles so that they
are released at the first part of the release cycle.
Vitamins and Buffers
Since the microorganisms also utilize vitamins such as thiamine,
folic acid, biotin, nicotinic acid, and the like, these can also be
included into the controlled-release products. It has been shown
that part per million concentrations, and in some cases a fraction
of a part per million, of vitamins can drastically increase
activities of the microorganisms and thereby increase speed of
waste degradation. For this reason, from 0.01 to 100 ppm by weight
of such vitamins may be included in the product.
Microorganisms also thrive best in particular pH ranges, such as
from about 6.5 to 8, so a buffering system may also be added to the
product to maintain the environment around the controlled-release
particle at these desirable pHs. This buffering system can be made
up of compounds which double as a nutrient source making the system
even more desirable. For example, the phosphate phosphorous sources
can provide buffering capacity into these desired pH ranges.
Representative buffers are a 1:1 mixture of KOH and KH.sub.2
PO.sub.4 and a 2:1 disodium phosphate and monopotassium phosphate
mixture.
Controlled-Release Coating
The controlled-release compositions of this invention are
particulate solid materials which comprise a water soluble core of
the nitrogen and/or phosphorus and/or sulfur micronutrient source
and optionally micronutrients and/or vitamins and/or buffers
surrounded by a release rate-controlling coating. While any of the
release rate-controlling membrane materials of the art, such as
those included in the above-referenced Theeuwes or Baker patents
can be used (these patents are incorporated herein by reference),
it has been found in our work to be advantageous to use a resin
formed from linseed oil and dicyclopentadiene (DCPD) copolymerized
and bodied. Such a composition is employed commercially under the
trademark "Osmocote", a trademark of Grace-Sierra Horticultural
Products Company. This material is described in U.S. Pat. No.
3,223,518 and Dutch Patent No. 132,686, both of which are
incorporated herein by reference. This "Osmocote" coating is
advantageous due to its low cost and high effectiveness when used
to create controlled-release products capable of lasting from one
week to 100 weeks. A typical remediation will last from 10 to 40
weeks.
Variation on the linseed oil/dicyclopentadiene system replaces part
of the linseed oil with soybean oil plus maleic anhydride and
pentaerythritol. These materials all function equivalently. More
specific examples of these materials include soybean oil at 60 to
65 percent and DCPD at 35 to 40 percent by weight; soybean oil at
35 to 40 percent by weight, linseed oil at 20 to 26 percent by
weight and DCPD at 35 to 40 percent by weight; and soybean oil at
55 to 60 percent by weight, maleic anhydride at 2 to 5 percent by
weight, pentaerythritol at 2 to 5 percent by weight and DCPD at 35
to 40 percent by weight.
Other types of controlled-release coatings which can achieve the
desired controlled nutrient release to bioremediation environments
include polyethylene, polypropylene, ethylene, propylene copolymer,
ethylene-vinyl acetate copolymer, vinylidene chloride, vinyl
chloride, vinylidene chloride-vinyl chloride copolymer, and
polystyrene. These materials are discussed in more detail in U.S.
Pat. No. 4,369,055 which is incorporated by reference.
Controlled-Release Nutrients
The macronutrients employed in the present process are typically
granular materials having grain sizes from about 0.1 to about 5 mm.
These granules will be composed of any macronutrient,
micronutrient, vitamin, and/or buffer previously mentioned or
amenable to being granulated and will be coated with a resin layer.
This coating will most likely be the linseed oil/DCPD copolymerized
resin and will be applied to the granules and then heat cured onto
the granules' surface creating a controlled-release film. The
amount of this resin applied to the granules will range from 1 to
20 percent by weight (based on the weight of macronutrients)
depending on the granules' shape and the required longevity of the
product. The typical percent of resin used will be between 5 and 15
percent.
Product Use In Bioremediations
In accord with the process of this invention, the precise amount
used will depend on the level of contamination being treated, the
concentration of background nutrients, the percentages of nutrients
in the controlled-release product of interest, and other conditions
affecting the nutrient release.
Typical use levels for soil treatment will run from about 0.50 to
about 50 pounds of controlled-release nutrients per cubic yard of
contaminated soil. We have found, quite unexpectedly, that even
though the release of nutrient is controlled and delayed, we get
best results at lower overall use levels than we observed for
non-controlled release (i.e., wholly soluble) materials. More
specifically, while soluble materials give best results at about 5
or 10 pounds per cubic yard, so as to obtain a contaminant
carbon:nitrogen:phosphorus atomic ratio of 100:20:1, we have
obtained far better results using as little as 1 pound of
controlled-release material per cubic yard of soil. On this basis
we prefer to use 0.25 to 5 pounds per cubic yard and especially 0.5
to 3 pounds per cubic yard.
In soil environments, moisture must be present to allow the
microorganisms to flourish. Moisture may be added if desired. The
controlled-release product may be spread on the contamination
and/or tilled into the contaminated soil. In the case of
contaminated aqueous environments, use levels of from about 0.0005
to about 0.5 pounds per gallon are advantageous, again this is
dependant upon the environmental conditions.
The environment being remediated can be the naturally occurring
soil or aqueous environment. Alternatively it can be a modified
environment wherein the modifications improve the rate or extent of
bioremediation. In the case of soil environments, this can include
turning over the soil, composting the soil, adding surfactant, or
slurrying the soil in a water medium.
In the case of an aqueous environment, the natural environment can
be groundwater, effluent from an industrial process or any other
waste water source. The improvement can include holding the water
in basins or ponds to assure adequate remediation time as well as
other improvements known to the art of water treatment
processing.
The bioremediation processes of this invention may rely upon the
microflora present in situ at the contamination site and this is
typically preferred. Alternatively microorganisms may be seeded
into the contamination site and these added materials can include
any of the organisms known in the art to affect contaminant
degradation such as the Pseudonomids, Methylotrophic bacteria,
Acinetobacter as well as a variety of anaerobic bacteria. It is not
intended that his invention be limited to any particular type or
family of organisms, including genetically engineered
microorganisms.
EXAMPLES
The invention will be further illustrated with reference to the
following examples. These examples are provided solely to
illustrate ways of practicing the invention, and are not to be
construed as limitations on the invention's scope, which is instead
defined by the claims hereinafter appended.
EXAMPLE 1
A nitrogen and phosphorus nutrient granule in controlled-release
form was prepared as follows. Granules each containing ammonium
nitrate, 80%; ammonium phosphates, 12%; calcium phosphates, 5%; and
inerts, 3% were screened to a Tyler mesh range of -6 to +12. This
material was then coated with 7.4% by weight (basis finished
product) of a linseed oil/DCPD copolymerized resin (6% w linseed
oil/38% w DCPD). The coating was accomplished by heating the
screened nutrient granules to approximately 70.degree. C., then
applying the resin at a flow rate which gives a uniform coating.
This controlled-release material had a nitrogen content of
approximately 28% and a phosphorus content of approximately 3.5%.
The release characteristics of this product, as found in the
laboratory, showed that the nutrients were released over a three
month period at 70.degree. F. The lab test consisted of
statistically splitting 8 grams of the controlled-release product
out of the bulk and placing it in a funnel containing approximately
200 ml of washed sand. The funnels were leached every seven days
with water and the leachate analyzed for nutrients.
This material was applied to soil contaminated with diesel oil. It
was predicted, using the old methodology of applying soluble
nutrients, that the bioremediation would take four months. The
contaminated soil was remediated in slightly over two months using
this controlled-release product. This material was also applied to
the beaches in Prince William Sound, Alaska, contaminated with oil
from the Exxon Valdez, and supplied nutrients continuously to the
indigenous microorganisms for approximately three months.
EXAMPLE 2
The preparation of Example 1 was repeated with the following
changes. After applying the controlled-release resin, a dispersion
containing micronutrients, vitamins, and a buffer was applied to
the granules and cured. The cured dispersion consisted of 20% resin
by weight with the remaining 80% consisting of phosphate buffer,
magnesium, iron, potassium, manganese, molybdenum, thiamine,
riboflavin, nicotinic acid, pantothenic acid, folic acid, biotin,
choline, inositol, and protein. This dispersion was then overcoated
with 0.5% (by weight of finished product) linseed oil/DCPD resin.
Also coated with this dispersion and then overcoated was a urea
substrate consisting of 25% urea granules coated with 11.1% resin
and the remaining 75% urea coated with 13.8% resin. This added urea
was then mixed with the micronutrient containing particles to
comprise 20% by weight of total product and created a product
containing approximately 29% nitrogen, and 3% phosphorus as well as
micronutrients.
This product was tested in a laboratory microcosm competing against
a dry soluble nutrient of comparable composition. At four weeks,
the bacteria population in the controlled-release nutrient treated
microcosm was an order of magnitude higher than the soluble
nutrient treated microcosm and two orders of magnitude higher than
the microcosm having no nutrient treatment.
EXAMPLE 3
The experiment of Example 1 is repeated with the following change.
The linseed oil/DCPD resin is replaced, using, instead, a resin
made from soybean oil, 57 percent; maleic anhydride, 2.5 percent;
pentaerythritol, 2.5 percent; and dicyclopentadiene, 38
percent.
EXAMPLE 4
The experiment of Example 2 is repeated with the following change.
The linseed oil/DCPD resin is replaced, using, instead, a soybean
oil based resin as described in Example 3.
EXAMPLE 5
Nitrogen and phosphorus nutrient granules, in controlled-release
form, are prepared as follows. Granules containing urea are
screened to a Tyler mesh range of -6 to +12. Granules containing
calcium phosphate, monobasic are also screened to a Tyler mesh
range of -6 to +12. 22.6 pounds of the urea granules are heated to
approximately 65 C. and 3.4 percent linseed oil/DCPD resin is
applied. Then 7.8 more pounds of screened, uncoated urea is mixed
into the 22.6 pounds of partially coated urea and the mix is
brought up to approximately 65.degree. C. After achieving this
temperature, 6.1 percent linseed oil/DCPD resin is added by weight
of substrate and resin. To conclude the coat 14.2 pounds of calcium
phosphate, monobasic acid is added to the partially coated urea
fractions and the temperature is brought up to approximately
70.degree. C. Resin is applied at 5.7 percent on the total weight
of the coated product. The final product contains 52.5 percent urea
coated with 13.8 percent resin, 17.5 percent urea coated with 11.1
percent resin, and 30.0 percent calcium phosphate, monobasic coated
with 5.7 percent resin. This product will supply nitrogen and
phosphorus continuously, in a ration of 5 to 1 respectively, for
three months in a moist environment kept at 20.degree. C.
EXAMPLE 6
A bioremediation field trial was conducted to determine if
controlled-release nutrients would enhance the degradation of
diesel when compared to the standard practice of applying dry
soluble nutrients. The results of the trial are presented in FIGS.
1-6.
The two controlled-release products were added at concentrations of
1, 5, and 20 lb/cu yard of soil. The first controlled-release
product used is referred to as Customblen.TM. 24-89 and contains
27.5% nitrogen and 8% phosphorus in P.sub.2 O.sub.5 form. The
second controlled-release product used is referred to as Max
Bac.TM. 2 and contains 26% nitrogen, 10.5% phosphorus in P.sub.2
O.sub.5 format, and 0.65% potassium in K.sub.2 O form. The
controlled-release products were prepared as described in Example 1
and Example 2 with the modification that the dispersion was coated
onto the substrate before the controlled-release membrane was
applied.
Two controls were present, one having no nutrient addition and one
having 3.5 lb/cu yard of a 30-9-0 soluble fertilizer with an
analysis of 16% ammonium, 14% nitrate, 3.27% water-soluble
phosphate P, and 3.93% citrate-soluble phosphate P.
The eight experimental conditions were identified as follows:
______________________________________ No nutrients A-series
Soluble farm at B-series 3.5 lb/cu yard Customblen .TM. 24-89 at
C-series 1 lb/cu yard Customblen .TM. 24-89 at D-series 5 lb/cu
yard Customblen .TM. 24-89 at E-series 20 lb/cu yard Max Bac .TM. 2
at F-series 1 lb/cu yard Max Bac .TM. 2 at G-series 5 lb/cu yard
Max Bac .TM. 2 at H-series 20 lb/cu yard
______________________________________
Each of the eight samples (one for each set of experimental
conditions) was run in triplicate 3'.times.3' plots. The pH of the
test plots was held at 6.5-8.0 by adding calcium carbonate.
Moisture was maintained uniform in that all the plots were treated
identically and allowed to vary uniformly between 20-60% moisture
during the tests. In each case, the initial concentration of
contaminants in the soil was approximately 2500 mg diesel per Kg
dry virgin soil. The test plots were troweled once per week to add
oxygen.
Samples were taken at 0 elapsed time, 1 month later and 2 months
later and analyzed for total bacteria, colony-forming units,
phenanthrene degraders (known hydrocarbon degraders), and
fluorescent Pseudonomids. The samples were also tested for levels
of total hydrocarbon and individual hydrocarbon fractions by carbon
number. Conductivity, as a measure of available nutrient
concentrations, was also measured on each sample.
As shown in FIG. 1, it was observed that the total bacteria present
in the samples remained relatively constant among all of the
samples with the exception that the high use levels (20 lb/cu
yard--series E and H) of controlled release products gave lower
bacterial levels than the 1 lb/cu yard or 5 lb/cu yard series
(series C, D and F, G). Similarly only modest differences were
noted in colony-forming unit concentration but with better
performance being seen with low controlled release nutrient levels
than at high levels. There were major differences in levels of
phenanthrene degrading bacteria among the 8 tests. The control with
no added nutrient was as much as two orders of magnitude lower than
the tests with nutrient. At high use levels (20 lb/cu yard--series
E and H), the added fertilizer first boosted and then depressed the
number of organisms observed. At low levels (1 and 5 lb/cu
yard--series C, D, G and H) the number of such organisms elevated
over time by as much as 21/2 orders of magnitudes and in several
samples as much as one order of magnitude greater than the standard
practice addition of soluble fertilizer. In virtually all cases
where nutrient was added, including the control, the level of
fluorescent Pseudonomids went up dramatically in the first month
and then fell in the second month.
The actual bioremediation performance observed with these eight
systems showed clearer advantages achieved by the present
invention. In FIG. 2 the measured levels of total diesel
contamination are plotted as a function of elapsed time.
The standard practice of adding dry soluble fertilizer reduced the
contamination to about 750 ppm in 100 days. Interestingly, high
loadings (20 lb/cu yard) of controlled release material gave poor
results. At this condition, over 1000 ppm of contamination remained
after 100 days. At a rate of 5 lb/cu yard, controlled release
material reduced contamination to about 250 ppm in about 100 days.
Best results were observed at the lowest rate of controlled release
material addition--1 lb/cu yard. At this condition, the
contamination was consumed the fastest and to the lowest level, 250
ppm.
Dirt samples initially containing added diesel contamination as
noted above were bioremediated under 3 comparative
conditions--condition A--no fertilizer, condition B--3.5 lb/cu yard
of dry soluble fertilizer and condition F controlled release
fertilizer at 1 lb/cu yard. Samples were taken at day 1, day 31,
day 53, and day 95 and analyzed by gas chromatography. The results
were digitized to give relative levels of each carbon number
fraction. FIGS. 3, 4, 5 and 6 show the results of these analysis
and illustrate a regular and striking advantage to the controlled
release material which allowed the clean up to achieve a reduction
in contamination to 16 units while the control was at 55 units and
the soluble fertilizer test gave 41 units.
* * * * *